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Stop Animal Exploitation NOW!
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"Exposing the truth to wipe out animal experimentation"

Government Grants Promoting Cruelty to Animals

The University of Chicago, Chicago, IL

ROBERT A. MCCREA - Primate Testing - 2006

Grant Number: 5R01EY008041-16
Project Title: Physiology of Oculomotor Premotor Pathways
PI Information: PROFESSOR ROBERT A. MCCREA,  [email protected] 

Abstract: DESCRIPTION (provided by applicant):
The aim of the proposed studies is to study the firing behavior of afferent inputs to the vestibular nuclei that are influential in modifying signal processing in vestibulo-ocular reflex (VOR) pathways during smooth tracking head movements and during near viewing. The initial studies will focus on the contribution of cerebello-vestibular pathways to these functions. Other possible sources of vestibular nucleus afferent inputs that modify signal processing in VOR pathways as a function of behavioral context will be considered if the cerebello-vestibular pathways do not appear to be sufficient to suppress the VOR during active head movements or for modifying signal processing in VOR pathways during near viewing. The first specific aim is to determine the source and characteristics of the head movement efference copy inputs to the vestibular nuclei that cancel or attenuate vestibular signals on secondary VOR neurons during gaze pursuit. Monkeys will be trained to pursue targets moving in the horizontal plane using smooth movements of the eye, head and/or body. Unit responses during active and passive movements will be compared. Regions of the cerebellum and brainstem that contain cells that are differentially sensitive to active head movements will be investigated further using electrical stimulation and chemical inactivation techniques. Anatomical studies will be carried out using retrograde tracers in combination with localized marking of recording sites to determine whether regions containing active head movement cells also project to the vestibular nuclei. The second specific aim is to determine the contribution of the cerebellar flocculus to viewing distance related changes in the angular and linear VOR during passive and active head movements. Monkeys will be trained to fixate or pursue visual targets presented on an earth stationary display mounted on a motorized track so that its distance can be varied from 10-150 cm. Vestibular stimuli will consist of passive whole body angular rotation or linear translation in head-restrained monkeys. Single unit recordings will be obtained from flocculus Purkinje cells and secondary VOR neurons. Unit responses to passive and active whole body motion at different viewing distances and target eccentricities will be recorded. The contribution of the flocculus to viewing distance related changes in the VOR will be assessed by examining the viewing distance related changes in the responses of Purkinje cells and VOR pathway neurons. Vestibular nucleus neurons that receive inputs from the cerebellar flocculus will be identified by electrical stimulation of the flocculus. Particular attention will be paid to determine whether different Purkinje cells are differentially sensitive to the movements of one or both eyes or to heave or thrust translation. The neurophysiological observations will be evaluated in the context of the observed effects of unilateral or bilateral inactivation of the cerebellar flocculus on the angular and linear VOR. The results should increase our understanding of the central mechanisms that allow clear vision of objects in a 3D environment during passive and active head movements.

Thesaurus Terms:
head movement, neural information processing, neurophysiology, vestibular pathway, vestibuloocular reflex, visual pathway, visual tracking
brain electrical activity, cerebellar Purkinje cell, neuroanatomy, neuron, smooth pursuit eye movement, visual field, visual fixation
Saimiri, microelectrode, single cell analysis

Fiscal Year: 2006
Project Start: 01-APR-1989
Project End: 30-NOV-2007

J Neurophysiol 92: 797-807, 2004. First published April 7, 2004

Context Contingent Signal Processing in the Cerebellar Flocculus and Ventral Paraflocculus During Gaze Saccades

T. Belton and R. A. McCrea

Department of Neurobiology, Pharmacology, and Physiology, University of Chicago, Illinois 60637
Submitted 4 March 2004; accepted in final form 30 March 2004

The methods used for recording and analyzing eye movements and single-unit activity in squirrel monkeys during combined eye-head saccades have been described previously (Belton and McCrea 2000a ,2000b ; McCrea and Gdowski 2003 ). All practices complied with National Institutes of Health principles of laboratory animal care (National Institutes of Health Publication No. 86-23).

Surgical preparation
Two adult squirrel monkeys were prepared for recording both single-unit activity and eye movements. A woven coil of fine, Teflon-coated wire (Cooner) was sutured to the sclera of one eye for recording eye movements using the magnetic search coil technique. A Plexiglas well was fitted onto the parietal bone for the placement of microelectrodes, and a metal reference pin was affixed to the skull adjacent to the probe insertion site.

Experimental recording conditions
Animals were seated in a Plexiglas primate chair atop a vestibular turntable (Inland 832). A harness that was fitted over the shoulders and in front of the trunk inhibited arm-raising and trunk-twist movements. A rod was attached to a keyed metal stud affixed to the occipital bone. The rod was coaxial with the rotational axis of the turntable and positioned within 5 mm of the C1C2 axis. It rotated within a low-friction ball bearing assembly fixed to the table, which allowed 45 head movements in the plane of the horizontal semicircular canals. A universal joint 5 cm above the head allowed pendular head position adjustments around the universal joint axis. The head could be reversibly fixed to the turntable by disabling the universal joint and blocking angular rotation of the vertical axis rod. The monkeys were trained to fixate and pursue a small visual target (0.5 W HeNe laser, <0.2 diam) projected onto a cylindrical, surrounding projection screen 90 cm distant from the monkey. The background presented by the screen was not an effective optokinetic stimulus during constant-velocity turntable rotations (3060/s). Target movement was produced with a pair of galvanometer-controlled mirrors mounted on the turntable. The animals were rewarded for fixation of the target using a sweetened milk mixture according to a variable reinforcement schedule. After training the monkeys were able to produce on-demand performance for sustained periods of 5 h, three to four times per week. Eye and head movements were measured using a magnetic search-coil system mounted on the turntable. These signals were low-pass filtered (510 kHz) and sampled (200500 Hz) at 16-bit resolution using a Cambridge Electronics 1401 data-acquisition system. Eye position was computed off-line as the difference between gaze and head position. Head- and gaze-velocity signals were created by digitally differentiating and filtering (low-pass smoothing, 2050 Hz) the position signals.

Please email: ROBERT A. MCCREA, [email protected] to protest the inhumane use of animals in this experiment. We would also love to know about your efforts with this cause: [email protected]

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Rats, mice, birds, amphibians and other animals have been excluded from coverage by the Animal Welfare Act. Therefore research facility reports do not include these animals. As a result of this situation, a blank report, or one with few animals listed, does not mean that a facility has not performed experiments on non-reportable animals. A blank form does mean that the facility in question has not used covered animals (primates, dogs, cats, rabbits, guinea pigs, hamsters, pigs, sheep, goats, etc.). Rats and mice alone are believed to comprise over 90% of the animals used in experimentation. Therefore the majority of animals used at research facilities are not even counted.

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